By Michael Erman and Christy Santhosh (Reuters) -Merck & Co posted higher third-quarter revenue on Thursday, as growth from its blockbuster cancer drug Keytruda offset falling sales from human papillomavirus vaccine Gardasil in China. However, shares fell nearly 2% after Merck lowered the high end of its revenue forecast for the full year. It now expects revenue of $64.5 billion to $65.0 billion compared with its prior view of $64.3 billion to $65.3 billion. J.P.Morgan analysts called the quarterly beat ...